: Mechanical advance
Sep 24th, 00, 07:37 PM
Could somebody please explain how to adjust the mechanical advance in my 68 Camaro 350. It has a vacuum advance HEI, and it currently is reading 20 degrees total at 2500 rpm with 12 degrees initial. I have been told that I should have around 36 degrees total. I have read a lot of posts on both this site and Chevelles.com and I still haven't grasped how to put more mechanical advance in. Is it the springs, stops, weights??? Anybody have a simple explanation on how to add 16 degrees to the crank???
Sep 24th, 00, 08:04 PM
Check it at rpm's above 2500, rev the engine up until it stops advancing.
See what that total advance is. and post it back here.
If you find that when you rev it up more, it advances enough, you just need to play with the spings on the advance weights.
Softer advance weight springs will make it come in quicker.
Search for posts by IgnitionMan and read them.
Check my web page for First Gen Camaro suspension info:
David's Homepage (http://ourworld.compuserve.com/homepages/David_Pozzi/)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Can Am Vintage Racer
[This message has been edited by davidpozzi (edited 09-24-2000).]
Sep 24th, 00, 08:19 PM
I have read most of Ignitionman's posts, on both sites. I am still confused. The total advance did not change from 2500 RPMs to 3500 RPMs. Any suggestions??
Sep 24th, 00, 09:19 PM
Mr. Gasket makes an HEI recurve kit. I believe it's part #929 if memory serves me correctly. You can buy it for under $10. It comes with new weights, springs and bushings and only takes about 15 minutes to install. You can start by using one of the light springs and one medium spring. This is where I had best results. It provided me with 26 degrees of mechanical advance all in by 3000 RPM (12 at idle, 38 total). When I used both light springs, there was not enough tension and the mechanical advance was already started at an 800 idle RPM, and only provided me with 18 degrees of mechanical advance. This may be one of the cheapest and easiest ways to start on your ignition. You can play with the different springs and even file the weights to provide different levels of mechanical advance. Other manufacturers also provide similar kits. See if that helps you and keep us posted.
Sep 24th, 00, 09:33 PM
Thanks for the info. I'll look into the kit.
Sep 27th, 00, 05:21 PM
Just finished working on my mechanical advance with great results. I tried a kit from Mr. Gasket but it didn't do much. Ignition Man posted a reply to my question a few days ago about HEI advance under the topic running recently about 56 total advance. He suggested trying to "back curve" the weights. I did this with an ordinary file with my old weights while both were mounted in the vise to get the same shape on both. It didn't take much to get a noticable bit of curve. I then used one light spring and one medium spring. Now I get about 22 degrees starting at about 1000 RPM and all in by 2500. Set 14 initial for a total of 36. Seem to work good.
Sep 28th, 00, 04:53 AM
My question is what does the advance stop bushing do on MSD distributors equipped with them? I am trying to get my engine set, I have a 1500-6500 rpm range with 3200 stall convertor and want to know when to bring in total advance and if stall speed has anything to do with the advance curve?
68 RS, Ash Gold,pwr windows,Hounds tooth
Sep 28th, 00, 06:20 PM
If Dennis will go for it, pics about back cutting the weight tail and HEI degree limit/plate are in the works. Will do and send this weekend/Monday.
Maybe a full tech article would be better???
MSD bushings will only stop the total of mechanical degrees, in crankshaft degrees, limit of the curve. The bigger the bushing installed, the less degrees available for mechanical advance. IE, bigger bushing, 20 degrees, smaller bushing, 24 degrees, etc. Springs then make the curve come in just where you want it, experiment.
Stock MSD garage door springs are for very, very stock engines. Make sure the spring set you end up with takes the mechanical advance all the way back down to idle timing and doesn't staer until after the idle rpms.
Sep 29th, 00, 07:11 AM
Thanks for the help I-man. Just trying to fully understand your reply. If I setup the mechanical advance as you have said, would I need to lockout the vacuum advance since you said to get the mechanical to go back to idle timing, or did you mean so that the weights are in all the way. I am working on a limiting plate for my vacuum canister.
68 RS, Ash Gold,pwr windows,Hounds tooth
[This message has been edited by CA420 (edited 09-29-2000).]
Sep 30th, 00, 03:48 AM
I tried the Mr. Gasket curve set the other day, and my total timing lowered, so I put the old set back in. I have plenty of room before the pins hit the stops so I may try what Iman recommended to wwind about backcutting the weights with a file. Also, the springs that were on my distributor seem to be a lot heavier than any of the ones in the set I bought. Thanks for the help.
[This message has been edited by rodsters (edited 09-30-2000).]